Altair Replica and Stuff
 

The computer itself is performing flawlessly. The 2SIO, Port 1 is perfect. I hooked it up to a terminal program on a PC and can run VTL-2. That's a neat language for taking so little memory. On Port 0, though, the Teletype prints the OK message but I can't type anything. I checked my cable wiring about thirty times then hooked the Teletype up to the PC and was able to communicate with the Altair32 emulator and a terminal program OK so I know the Teletype is good. Any ideas what could be wrong? Did you have a 20mA machine there to test Port 0? If so it worked for you, right? Thanks again for your obvious care in the assembly and packing of this machine. I can't wait to get the Port 0 problem fixed and to get my ACR board from Grant.

No, unfortunately I don't have any current loop devices. I did verify that the 6850 was working correctly by connecting a TTL/RS232 adapter to its Tx/Rx pins, so if there's a problem it must be with the 7404 inverter (IC K, pins 8,9) or something on the incoming side (pin 9) of that. Do you have any way of testing whether a reasonable signal is getting to pin K9?

Geoff.

Hi Guys. I did not get my teletype working, but now you have inspired me. Sorry, Tom, but I cannot help you yet but perhaps I can if I get mine working.

My problem is that I do not know if my teletype is current loop or RS-232. Do either of you know how I can figure this out? Are there pin voltage settings I could measure? I've always held off because I did not want to take any chances of frying my 2SIO port or my teletype. Would a wrong (mismatched) connection cause harm?

Paul

Unfortunately, being a software person, I wouldn't even know what a reasonable signal is. Since the 7404s are socketed, would it help if I swapped them and see if the problem follows the current K chip?

2SIO Failure
 

Well, I swapped the two inverters. The problem stayed where it was, the first port only. So both inverters are good. (You probably already knew that.) Where do I go from here?

TIA

Tom Lake

Tom,

You said earlier that you checked the teletype by connecting it to a PC. Does that mean you have a current loop port on your PC?

Geoff.

Yes. I have an Advantech PCI-1603 2-port PCI board where either port can be configured as either RS-232 or 20mA Current Loop (sound familiar?) by setting jumpers on the board. I bought it specifically to run the Teletype with the Altair32 emulator until I could get Grant's replica. It works great!

BTW are there instructions somewhere for using the monitors, DBL, MBL and music ROMS I got with my system? I tried to load 4K BASIC into the replica using your instructions for the TeraTerm terminal emulator but have been unsuccessful. If I could use the MBL ROM to do it, I'd save having to enter the bootloader each time That's the point of the MBL ROM, no? 8^) Thanks again for your patience!

Tom L

You can check it without connecting it to your Altair. Plug in the Teletype to the AC outlet. Turn the Line/Off/Local knob to Line (all the way counterclockwise if you don't have the front aluminum escuheon). If the TTY starts chattering without printing anything, it's 20mA Current Loop. If it stays silent, it's RS-232. Here's another tip: Don't leave the Teletype plugged into the power line when not using it. Even when off, there's a board inside that stays powered on and gets hot enough to scorch the plastic case. It will significantly shorten the life of your unit.

Tom Lake

I'm not sure how to use the AdvMon. I got it to respond to 5 commands: Mxxxx, Wxxxx, Exxxx, Rxxxx, Gxxxx, where xxxx is a 4 digit hex address. The only one that did anything useful for me was M which displays a hex dump starting at xxxx, one line at a time. Press space for another line, return to quit.

Yes, you definitely want to use MBL instead of toggling a loader in each time. I tested the PROMs on your machine with my 2SIO and got 4k basic to load. You have to play some games with the front panel switches because 4kBasic interprets the sense switches differently from MBL, but it's still easier than entering a 1st stage loader each time. We can go over that when we get the port working.

Just out of interest, did you try entering the simple echo routine on http://www.solivant.com/altair_bootl...oaders&pagen=1 ? If that won't work correctly we're not going to get VTL, MBL or anything else working on that port.

Geoff.

I tried it, just to see if my input problem on port 1 is a hardware problem or a problem with VTL-2. It's a hardware problem. I can't use the first port for input. If I change the IO port references iin the code to the second port, it works OK.

Tom L